It is well known to utilize a ceramic coating to improve the corrosion resistance and mechanical durability of a gas/combustion turbine component. The demand for continued improvement in the efficiency of such turbines and combined cycle power plants has driven the designers of these systems to specify increasingly higher firing temperatures in the combustion portions of these systems. Although nickel and cobalt based superalloy materials are now used for components such as combustor transition pieces and turbine rotating and stationary blades in the hot gas flow path, even superalloy materials are not capable of surviving long term operation without some form of insulation from the operating environment.
It is known to coat a superalloy metal component with an insulating ceramic material to improve its ability to survive high operating temperatures in a combustion turbine environment; see for example U.S. Pat. No. 5,180,285 issued on Jan. 19, 1993 to Lau, and U.S. Pat. No. 4,576,874 issued on Mar. 18, 1986 to Spengler, et al, both incorporated by reference herein. One thermal barrier coating system in common use today is a yttria stabilized zirconia (YSZ) top coat applied to a super alloy substrate structure, often with an intermediate bond coat such as MCrAlY, where M may be nickel, cobalt, iron or a mixture thereof. However, even YSZ coated super alloy components are not capable of withstanding long term operation at the operating temperatures of the most modern and efficient engines where combustion temperatures may exceed 1,400 degrees C.
Accordingly, it is an object of this invention to provide an improved thermal barrier coating for the hot gas flow path components of a modern combustion turbine system. It is a further object of this invention to provide a component for a combustion turbine capable of long term operation in the high temperature, highly corrosive environment of the most modern of combustion turbine engines.